There is a book about this, and other things that animals would tell us if we knew how to listen to them. The book is "If Only We Would Listen" by Julie Bristoe. She mostly writes about goats, but it would apply to other species just as well.

Yes, animals do mourn. They understand a lot more than we give them credit for, and they want to know what's going on. If one of their friends or member of their family dies, and they just don't see them again, they have a hard time with that and will keep looking. They seem to cope better if they know what happened. It makes sense. Look at what people will do and what they go for trying to find out what happened if someone they love is missing. We all need closure so that we can grieve properly, and if we don't grive properly we never can really move on.

Rap